an epidemiological study of listeriosis in dairy cattle

and meat products have resulted in an enormous number of publications (Johnson and
others 1990, Jay 1996, Kozak and colleques 1996, Beuchat 1996).
L. monocytogenes has frequently been isolated from soil, vegetation such as
corn, soybean plants, grass (Welshimer and Donker-Voet 1971, Weis and Seeliger
1975), sewage sludge (MacGowan and others 1994), river waters, industrial effluent
such as abattoirs, cattle market, poultry packing plants (Watkins and Sleath 1981),
vegetables such as cabbage, cucumbers, potatoes, radishes (Beuchat 1996), salads
containing cabbage, carrots, lettuce, cucumber, onion, leeks, watercress, celery and
fennel (Sizmur and Walker 1988).
Jay (1996) reviewed the overall prevalence of L. monocytogenes in meat and
meat products by combining the results of several studies. The prevalence in meat (fresh
or frozen) was 20% in pork, 16% in beef and lamb and 17% in poultry. He also
estimated a 13% overall prevalence for processed meat such as sausages, bacon, salami,
pate and corned beef.
Kozak and colleagues (1996) reported the prevalence of L. monocytogenes in
raw milk in the same way as Jay. It was 3.1% in the USA, 2.7% in Canada and 4.1% in
Europe. In a national survey carried out in England and Wales by Greenwood and
colleagues (1991) L. monocytogenes was isolated from 3.6% of raw milk samples.
Fenlon and Wilson (1989) examined bulk milk tank for the presence of L.
monocytogenes in Scotland over a period of time and found that 3.8% of samples were
positive for L. monocytogenes. In another study Fenlon and colleagues (1995a) isolated
L. monocytogenes from 25 of 160 bulk milk tank samples. L. monocytogenes
organisms occur in low number in milk and are easily killed at pasteurisation
temperatures (Farber and Peterkins 1991, Kozak and colleagues 1996). However, the
isolation of L. monocytogenes in pasteurised milk and in several milk products such as
cheese, ice cream, yoghurt, (Greenwood and others 1991) suggest that post
40